There are generally three types of refrigerators having freezing and cooling compartments. There is the conventional one-door refrigerator with the freezing compartment within the body of the refrigerator, the conventional cycle defrost refrigerator, where the freezing compartment is separated and automatic defrost is effectuated only in the cooling chamber and a frost-free refrigerator having two compartments, where both compartments are automatically defrosted.
The frost-free refrigerator is expensive to construct and to operate.
The cycle defrost refrigerator only defrosts the evaporator of the cooling compartment, thus, full defrost of a cycle defrost refrigerator requires a shut down of the refrigerator for an ultimate defrost. The system may also require the addition of heat to properly defrost. The cycle defrost system is inconvenient. The requirement to provide two connected evaporators adds cost to the system.
The conventional frost-free refrigerator requires expensive construction, including heating elements near the freezer doors to make certain that the freezer does not sweat and is never frozen shut. A freezing compartment within a conventional refrigerator does not pose this problem. Defrosting the frost-free refrigerator is also expensive, since it generally requires the application of additional heat in order to remove the frost. The frost must be removed quickly, in order to minimize the warming of the contents of the freezing compartment and warming the contents of the cooling compartment.
The conventional one-door refrigerator with a freezing compartment within the body of the refrigerator may be defrosted by automatic cycle defrost or defrosted by a shut down. The one-door refrigerator with a freezing compartment within the body of the refrigerator has the efficiency advantage of requiring less insulation to protect the freezing compartment and is thereby generally less expensive to construct and somewhat more energy efficient. It has the disadvantage of requiring more frequent defrosting than the freezing compartment in the cycle defrost refrigerator.
Prior art systems for fully automatic cooling and defrosting, generally require extensive fan circulating means to circulate the air within the refrigerator for the purposes of controlling both cooling and freezing compartment and the installation of heaters and expensive wiring to defrost the evaporator and portions of the condensate disposal system. Frost-free systems also require a defrost timer and defrost heater control and associated wiring.
The present invention efficiently defrosts the evaporator within the refrigerator, primarily circulating the air within the refrigerator without need for the addition of the defrosting heat. It does this by circulation of internal air primarily by convection, or with a minimum intervention of fan-blown air.
A distinction of the present invention is a single evaporator element serving a self-defrosting frost-free cooling compartment and freezing compartment in which the evaporator is located above the frozen food chamber. The single evaporator element may be contained in an insulated compartment.
While reference herein will be made to the conventional evaporator and compressor on and off cycles, the present invention is equally applicable to other refrigeration elements and their on and off cycles, independent of refrigeration employing a compressor.